Why Is My Furnace So Loud and How Do I Fix It?

If your furnace is making unusual and loud noises, it’s important to pinpoint the source of the sound in order to solve the issue. Noise can indicate a much more serious problem or even damage in the unit. There are many different parts that can cause noises to occur — each producing a different noise.

Furnace noises should not be ignored. But due to how loud the noises usually are, they would be hard to ignore even if you wanted to!

We help break down the different sounds, and what you can do to fix it.

Loud Furnace Causes & Solutions

Blower Motor

If you are hearing loud screeching and rattling noises when you turn your furnace on, the bearings in the blower motor or the blower motor itself could be to blame. Your blower motor forces the warm air out of your furnace and through the air ducts in your home. The blower motor needs routine lubrication, and often a specific kind of lubrication to upkeep performance and function over time. Otherwise, the fan might seize up and cause a loud noise (and an even louder repair bill).

If you are knowledgeable of the process, you can add lubrication to the motor. This is an in-depth DIY project requiring careful motor removal. In most cases, it’s best to contact a professional technician to for a proper inspection, oiling, and any other necessary repairs or maintenance.

Loose or Damaged Blower Belt

If your furnace has a belt-driven motor, when the blower belt becomes loose, a squealing or similar sound can ensue. Another reason for squealing can be linked to shaft bearings and other moving parts becoming dry. During bi-annual tune-ups, a professional technician lubricates moving furnace parts in order to keep your furnace in peak performance mode all winter long.

Over time, your blower belt will need to be adjusted or replaced. While it’s possible to adjust the fan belt on your own, never attempt to replace a damaged blower belt on your own. It’s best to contact a professional to inspect the fan belt and provide the necessary adjustment, repair, or replacement.

Blower Wheel

Loud clanking or scraping, classified as a metal-against-metal sound signals a serious problem with the furnace’s blower wheel. Most likely the blower fan has become loose and is creating the sound by hitting against the blower house casing.

A metal-scraping sound needs to be addressed right away and requires the attention of a professional HVAC technician. When you hear a metal-against-metal sound, turn off your furnace immediately, and contact a qualified HVAC technician for a complete system inspection. Do not continue to run your furnace if you are hearing loud metal-against-metal or scraping sounds.

At best, the wheel is only slightly damaged, and the repair will be minimal, at worst, the blower fan is broken and will need to be professionally replaced. A professional diagnosis is necessary to determine course of action. Contact Service Champions for fast, full-service furnace services.

Dirty Burners

If your furnace has dirty burners that need to be cleaned, you could be hearing a loud bang or boom when you turn your furnace on. Dirty burners are dangerous because they can delay the ignition. A delayed ignition causes gas to build up and go “boom” or “explode” when the ignition is turned on. Annual inspections and cleanings will keep this issue at bay. During a professional tune-up, all furnace burners are inspected and cleaned.

The other cause of a loud bang or boom that reverberates throughout the home is an unbalanced air-to-fuel ratio. In order to work properly and efficiently, your furnace needs a proper mixture of air and gas. If you have too much air and not enough gas, gas can build up resulting in a loud booming sound.

Regardless of if you have dirty burners or a unbalanced air-to-fuel ratio, you will want a professional to inspect the situation and provide the proper cleaning and adjustments.

A thud or boom sound could also simply be the metal air ducts expanding and contracting as the temperature changes. This is natural and does not indicate any damage to the furnace. If this becomes too bothersome, there are some solutions you could discuss with your local professional HVAC company, such as duct sealing and insulation, duct replacement, and air filter replacement.

Faulty Heat Exchanger

If you are hearing rattling noises coming from your furnace, then it could just be letting you know there is a loose panel or a loose screw. You can attempt to handle this yourself by first turning off power to your furnace at the source. Then, using a screwdriver, you can tighten your panel. This might just rectify the rattling. Also, make sure the access panel is fully secured.

However, if the rattling is not from a loose screw or access panel, it is much more serious and dangerous. Rattling can be a sign of a faulty heat exchanger. There might be a leak or crack in the heat exchanger.

One of the main causes of a cracked heat exchanger is a lack of airflow. If airflow is restricted from dirty filters, blowers, and coils, heat can build up within the heat exchanger and cause cracks and splinters. This usually happens when the furnace has been neglected for a long period of time.

This can lead to carbon monoxide leaking into your home. A professional technician should be contacted immediately if the rattling noises from your furnace are not squelched by tightening some screws.

Common loud furnace noises:

  • Loud scraping
  • Metal against metal
  • Humming
  • Screeching
  • Rattling
  • Pop or Bang
  • Rumbling

Never ignore any of these scary furnace noises! Contact a professional HVAC technician as soon as you notice them. And don’t forget to schedule annual furnace maintenance at the beginning of every heating season to keep your furnace safe and efficient all year long. Consider signing up for a home maintenance plan to make sure you never forget about this important home maintenance task.

In order to fix furnace issues and quiet unwanted furnace sounds, contact a professional Service Champions technician. We’re available 24/7 throughout the East Bay, South Bay, and Sacramento areas.

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